JPH03125665A - Steering device - Google Patents

Abstract

PURPOSE:To improve steering rigidity and high-speed straight advancing property by installing a spring member for adding a pressing force of a specified numerical value or more to a retainer opposed to a rack, and polishing mutually engaging rack tooth and pinion after their respective thermal treatments. CONSTITUTION:On the inside of a housing or hollow guide member 10, a rack 11 is mounted in such a manner as to be capable of axially sliding. A rack tooth engaged with a pinion 12 is formed on part of the rack 11. In the above constitution, a retainer 13 in contact with the circular part on the opposite side of the rack tooth of the rack 11 is received in the housing 10. A compression coil spring 14 is installed to the retainer 13, whereby the retainer 13 is energized toward the rack 11. In this case, the energizing force is specified to 35Fgf or more. At least the center part of the rack tooth and the pinion 12 are polished after their respective thermal treatment.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a rack and pinion type steering device,
In particular, the present invention relates to a highly rigid steering device that improves straight-line performance during high-speed driving.

(Prior Art) A type of steering used to change the direction of travel of an automobile includes a pinion connected to a steering wheel (steering wheel) and a rack having rack teeth that mesh with the pinion. There is. Usually, the rack is slidable in the axial direction by a cylindrical guide member, and in the case of power steering, a power cylinder is integrated with this guide member. Further, as shown in Japanese Patent Application Laid-Open No. 58-221767, a retainer is incorporated into this guide member in order to apply a pressing force to the rack from a portion opposite to the rack teeth. ing.

(Problems to be Solved by the Invention) There is a limit to the force with which such a retainer can press against the rack. This is due to the accuracy of the rack teeth and pinion tooth surfaces used in conventional steering.
It is thought that not only will the tooth surfaces wear out due to friction between the tooth surfaces during steering operations, and sufficient durability cannot be maintained, but also that the steering force of the driver will increase during steering operations.t'LfS
It is from.

In the case of buff steering, this steering force is assisted by a hydraulic pump, but there is a problem in that as this steering force increases, the load applied to the pump also increases.

By the way, in addition to the above-mentioned power steering, even in normal steering that does not have the auxiliary force of a hydraulic pump, in the case of a type of steering that has a rack and pinion, the pinion and rack teeth are conventionally machined separately. These racks and pinions are then heat treated, and in some cases, they are ground after cutting, but the heat treatment is the final process to complete these racks and pinions.

Various experiments and research were conducted to improve the steering response of this type of steering device when driving straight at high speed. As a result, the shimmy phenomenon that conventionally occurs when traveling straight at high speeds is considered to be due to torque fluctuations occurring during steering, since there is a limit to the stiffness of the steering due to the presence of backlash between the rack and pinion. found.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to improve straight-line driving performance during high-speed driving by improving steering rigidity.

(Means for Solving the Problems) To achieve the above object, the present invention provides a rack having rack teeth, which is connected to wheels at both ends thereof, is supported slidably in the axial direction by a guide member, and has rack teeth. In a steering device having a pinion that meshes with rack teeth and is connected to a steering wheel, a spring member that applies a force of 35 Fgf or more to the rack is attached to a retainer that contacts the rack on the opposite side of the rack teeth. In the steering device, at least the center portion of the rack teeth and the pinion are respectively heat-treated and then ground.

(Function) In the present invention, at least the central portion of the rack teeth and the pinion are cut, then heat treated, and the tooth surfaces are further ground. The backlash of the meshing part is reduced, and as a result of the fact that a strong pressing force is applied to the rack by the retainer, a highly rigid steering device is obtained, and particularly good high-speed straight-line performance is obtained. In particular, it has been found that the idle rate of the meshing efficiency between the pinion and the rack is significantly smaller than the positive efficiency in a range where the rack axial force is small, that is, a range where the steering angle is small. This means that wheel vibrations and the like are not transmitted to the steering wheel, resulting in good high-speed straight running performance, shimmy, and release-convergence performance.

(Examples) Hereinafter, the present invention will be described in detail based on Examples of the present invention.

Figure 1 shows the rack 11 and pinion 1 in the steering wheel.
As shown in FIG. 1, a rack 11 is mounted in a housing, that is, a hollow guide member 10, so as to be slidable in the axial direction. A part of this rack 11 has rack teeth 11a that mesh with the pinion 12.
have.

The rack teeth 11a and the pinion 12 are teeth that should have a predetermined helix angle.

FIG. 2 is a cross-sectional view taken along the line ■-■ in FIG. 1, and the housing 10 houses a retainer 13 that abuts the arcuate portion of the rack 11 on the opposite side of the rack teeth 11a. A compression coil spring 14 is attached to the retainer 13, and the spring 14 applies a predetermined spring force W toward the rack 11 to the retainer 13.

This spring force W was conventionally less than 20Kgf, but
In the case of the present invention, the value is set to 35 Kgf or more.

FIG. 3 is a diagram showing the processing procedure for the pinion and rack teeth of the present invention, in which the pinion is cut by hobbing, then heat treated, and finally the tooth surface is ground by a grinder. Similarly, racks are cut using a broaching machine or the like, then heat treated and the tooth surfaces are finally ground. In this way, by finally grinding the tooth surfaces, the pinion and rack achieved highly accurate meshing with little picklash.

Since the meshing between the pinion 12 and the rack 11 can be set with high precision as described above, the force applied by the retainer 13 to the rack 11 is set to 35, and the force applied to a force higher than gt is set to 35.

Conventionally, this pressing force had to be set to 20 gf or less because it was not possible to reduce the backlash value, but in the present invention, this pressing force was set to 35 kgf or more. By setting this to a high value, we were able to create a highly rigid steering system.

FIG. 4 shows data showing the relationship between the excitation frequency applied to the steering wheel and the shimmy level (dB) generated thereby for the conventional steering wheel and the steering wheel of the present invention. When pressing, force W is 40! llf, and conventionally its value was 20Kg.
It is set as f. This shimmy level (dB) is 20100
It is determined by (wheel tangent g/rack axis input).

FIG. 5(A) is a graph showing the meshing efficiency between the rack and pinion of the present invention, and FIG. 5(B) is a graph showing the meshing ratio in the conventional steering structure.

Here, the positive efficiency ηP and the floating rate ηR are defined as follows.

77P = (CO3an +1t1AtanβR)/
(CO8an 10μI AtanβP)77R= (C
O8an ul Atan 13P ) /(CO3
an -μl AtanβR) where A= (Pn
+W/SIN an ) /Pn, βP is the torsion angle of the pinion, βR is the torsion angle of the rack, an is the normal pressure angle, Pn is the tooth surface normal load, and μm is the tooth surface friction coefficient.

In the present invention shown in FIG. 5 (A), the retainer pressing is performed when the force W is set to 40 KCI, and FIG. 5 (B)
In the conventional structure, the force is 20K (II).As is clear from this data, in the steering of the present invention, in the range where the rack axial force is small,
It becomes clear that the migration rate is low.

Figure 6 shows data showing the reverse input no-load steering force based on the relationship between the rack axial force and the rack stroke for the steering device of the present invention and the conventional steering device, and shows that the rack stroke is In a small range,
In FIG. 5 (A>), it is shown that the floating rate is smaller than the positive efficiency, and the high-speed straight running performance, shimmy phenomenon, and release convergence properties are also good.

Note that all of the rack teeth 11a are not subjected to tooth surface grinding after heat treatment, and only the center portion of the rack teeth, that is, the portion of the teeth corresponding to the steering angle of the steering wheel 18 within a range of ±45°, is processed. It is also possible to perform tooth surface grinding after heat treatment (effect of the invention).As described above, pressing the retainer against the rack requires a force of 3
A force of 5Kgf or more is applied, and at least the central part of the rack teeth and the pinion are ground after being heat-treated, increasing the rigidity of the steering and minimizing backlash. As a result, torque fluctuations were reduced, steering response was significantly improved, and the shimmy phenomenon was reduced. In particular, the effect of reducing the shimmy phenomenon was remarkable when traveling at high speeds, and smooth steering was obtained when traveling at normal speeds.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing a rack and pinion type steering device of the present invention, Fig. 2 is a sectional view taken along line I-I in Fig. 1, and Fig. 3 forms a meshing part of the present invention. A process diagram showing the process, Figure 4 shows data showing the characteristics of the steering of the present invention in comparison with conventional steering, and Figure 5 (
A) and (B) are data showing the efficiency of the steering device of the present invention and the conventional steering device, respectively, and FIG. 6 is a graph showing the no-load steering force of reverse input. 11...Rack, lla...Rack tooth, 12...
Pinion, 13... Retainer, 10... Guide member.

Claims (1)

[Claims] In the steering device, the steering device includes a rack having rack teeth, which is connected to wheels at both ends thereof, is axially slidably supported by a guide member, and has rack teeth, and a pinion that meshes with the rack teeth and is connected to the steering wheel. A spring member that applies a pressing force of 35 Fgf or more to the rack is attached to a retainer that contacts the rack on the opposite side of the rack teeth, and at least the central portion of the rack teeth and the pinion are respectively heat-treated and then ground. Steering device.